Earlier: The Supreme Court is expected to announce a ruling on Obamacare Thursday, deciding the fate of millions of Americans' health insurance, but how will the SCOTUS ruling on Obamacare affect birth control costs? The case, King vs. Burwell, challenges an IRS rule that provided health insurance subsidies for low-income people through federal exchanges in states that didn't set up their own Affordable Care Act marketplaces. The plaintiffs argued that the law only allows subsidies through state exchanges, not federal exchanges. Since two-thirds of the country didn't set up separate state marketplaces, the decision will affect millions of people.

Because subsidies are based on income, a loss of subsidies would affect the poorest women in the country. Research by the Roosevelt Institute found that Obamacare increased the number of birth control prescriptions filled without co-pays from 1.3 million to 5.1 million in 2013 and the percentage of women who had access to no-cost birth control grew from 14 percent to 56 percent. Only 16 states and Washington D.C. currently have their own state-run marketplaces, so women living below the poverty line in the other states will lose their subsidies if the Court doesn't side with the Obama administration.

If SCOTUS decides subsidies can be provided in states with a federal marketplace, birth control costs won't change. If you currently have a subsidized health insurance plan, you'll keep it — regardless of what state you're in — so your birth control will continue to be low-cost or free.

However, if the Court rules against the Obama Administration, women's health coverage will drastically change. While the decision won't directly affect birth control costs or co-pays, it will make health insurance premiums more expensive for people with subsidies by as much as 650 percent, according to U.S. News & World Report. The Department of Health and Human Services said 6.4 million Americans could lose their health insurance subsidies, which will make their health coverage completely unaffordable.

The millions of women who will potentially lose their health insurance will in turn lose their current affordable birth control. According to Planned Parenthood, that could be as many as 4 million women, with about half of them located in Florida, North Carolina, Georgia, Pennsylvania, and Texas. Without insurance, these women will be forced to pay out-of-pocket for their contraception. If you currently have a subsidized health insurance plan under Obamacare and you live in a state that operates through a federal marketplace, you might have to pay a lot more for birth control very soon.